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abrasive flow machining media

In the first approach, an intimately interpenetrating second phase may be introduced during or following basic polymer manufacturing. The finely divided particles may begin from the smallest sizes available up to about a 4/6 sieve size, with the median particle size not to exceed about 0.5 cm, with larger particles to be used only in exceptional and unusual circumstances. Guar gum based medium cannot achieve very high viscosities, dries out over time and is not particularly durable. In a particularly preferred embodiment, silicone- or polyorganosiloxane-based medium contains elastic silicone rubber particles dispersed therethrough to achieve increased relaxation times comparable to those attainable with the inclusion of a thermoplastic polymer. It should be borne in mind that the abrasive used will be varied to suit the individual application. Available with different size of media cylinders: 8 (200mm), and 10 (250mm), Gradnings- & Maskinteknik AB, Box 2180, S-750 02 Uppsala, Sverige, Tel: 018-15 83 16. A carrier with a high percentage of polymer will be stiff and can be used to polish or radius large features; a carrier with a high percentage of lubricant will be soft and flow easily through small or long passages. Additional preferred thermoplastic polymers for the purpose of the invention are the styrene polymers and copolymers which are gel-like (and elastomeric) in consistency at ambient temperatures (24 C.5 C.). The carrier in this abrasive media has only 35% by weight polymer, so it is much softer and more flowable than the previous example. This feature of the current composition and method enhances performance in various applications. Alternatively, at low percentage inclusion and with a significant percentage of mineral oil or other liquid carrier, the thermoplastic polymer abrasive flow medium can be formulated to achieve viscosities significantly lower than those of traditional media for honing applications where a more fluid carrier is preferred. In applications in which a silicone- or polyorganosiloxane-based viscoelastic material base is not contraindicated, surprisingly it has been found that a good particulate elastic material for inclusion is silicone-rubber in particulate form, even though silicone rubber and silicone rubber derivatives are not thermoplastic polymers. Particle size selection is peripheral to the present invention, which improves traditional media with either a non-silicone additive or a non-silicone thermoplastic polymer substitute altogether. There is a need for economic media because commercial media cost is too high (Rs2.5 lakhs/kg), available only in three standard forms and supplied by only one company (Extrude Hone Corporation). Enhanced elastomeric characteristics enable more uniform abrasive machining. The elastomeric material tends to contribute extremely long relaxation times while the much more flowable viscoelastic material would contribute relaxation times that can be much shorter than the residence time of the media within the passageway during abrasive flow processing. Quantities of medium prepared in accordance with Example 3 were passed through the interior length of a tube as shown in. Another way of appreciating the present thermoplastic component is to understand that it enables more uniform abrasion throughout the length of a larger LID passage by engineering the relaxation time of the media to match more effectively the passage dimensions and flow rate while retaining desirable viscous flow behavior. abrasive nptel afm sensitivity percentual In a particularly preferred embodiment, silicone- or polyorganosiloxane-based medium contains elastic silicone rubber particles dispersed therethrough to achieve increased relaxation times comparable to those attainable with the inclusion of a thermoplastic polymer. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). The results of the study confirm that the performance characteristics attributed to the non-silicone content of the test media contrasted and complimented that of the silicone-based media content. To further increase flowability, the abrasive content has also been lowered to only 30% by weight. In other words, the elastomeric constituents enhance the elastic component of the viscoelastic behavior of the media while preserving the beneficial presence of a viscous-flow behavioral component. The carrier, or media base, is a viscoelastic semi-solid, which can range in viscosity from a firm putty-like material to a soft, almost grease like consistency. abrasive machining When machined, cast, or other parts are complex, the challenges of polishing increase, because the presence of one or more intersecting bores, flats, slots; key ways or splines often produces a sharp corner or a raised burr at the point of conjunction. In certain embodiments, the thermoplastic polymer is added to the media in the form of discrete elastomeric particulates, which elastomeric particulates are in many cases the same size or smaller than the abrasive particles coadmixed therewith. One part by weight of the resulting admixture was combined with two parts by weight of aluminum oxide, 100 grain size. PATENTED CASE, Owner name: Abrasive media will contain from a low of around 25% up to around 67% by weight abrasive grain. This would be a heavy and aggressive media, which would be suitable for polishing the internal passages in large cast industrial closed pump impellers. In typical abrasive media applications, particulate or pelleted thermoplastic polymer starting material is obtained commercially and, prior to use, is liquified by elevating its temperature to between about 185 F.-375 F. The styrene-butadiene copolymers may be incorporated in the medium between 0.001-100%, more preferably 0.25-100% and most preferably between 0.5 and 100% by weight. This review provides a vision into the various media in AFM and creates an improved understanding of finishing processes, to help in the selection of optimal machining limitations for the surface finishing of wide-ranging workpieces in practice. However, this styrene block copolymer is exemplary only and virtually any other thermoplastic polymer having the same elastomeric and viscosity characteristics within the application temperature may be used. Extended relaxation time is particularly useful in abrasive flow machining of passageways having longer length/diameter (L/D) dimensions. afm abrasive machining extrude hone extrudehone Ninety-five parts by weight of food grade white mineral oil were combined with 5 parts by weight of KRATON styrene-ethylene/butylene-styrene block copolymer at a temperature of approximately 225 F. The components were blended in a vessel provided with a manual stirring blade. The abrasive grain is a single size, a finer 80 mesh silicon carbide, and the abrasive content is 50% by weight. Various grades of mineral oil or paraffin oil may also be used to plasticize and/or to dilute the thermoplastic polymer media. The elastic nature of the media base supports the abrasive grain as it flows across surfaces or through internal passages to refine surfaces and edges with a pure grinding type action. Furthermore, the pure non-silicone media also proved effectively to machine, with abrasive flow, the tubular passageways of the work pieces. The exemplary KRATON thermoplastic polymer is available, for example, as G1650 and G1651 SEBS block copolymers from Shell Kagaku. Many types of products, from automotive parts to prosthetic implants, after molding or machining require finishing operations such as polishing of the various formed surfaces. With ONE WAY FLOW Abrasive Flow Machining, the abrasive media fl ows through the tooling and workpiece in only one direction. The resulting mixture presented enhanced elastomeric characteristics over the silicone medium alone and, upon testing with addition of abrasive particles more, achieved even distribution through internal fabricated article passages. Such polishing is complicated enough when the surface to be honed is easily accessible. The presence of thermoplastic polymer imparts a greater elastomer characteristic (elasticity, compression resistance) to the medium compared to that of traditional media such as silicone or water-based gel media. Although any type of free abrasive grain can be blended into the carrier, the most commonly used abrasives are silicon carbide and aluminum oxide. 3,819,343 and No. Traditionally in the practice of abrasive flow machining (AFM), the medium is comprised of either a silicone rubber composition, or other extrudable materials such as a water-based gel polymer, in a continuum of viscosities ranging from putty-like to near-fluid viscosities. When silicone rubber particles are used in place of the thermoplastic polymer particles discussed elsewhere in this specification, they generally meet the same size parameters. After mixing the liquified KRATON and lubricating grease but prior to cooling, equal parts by weight of the mixture and a traditional silicone rubber (polyorganosiloxane polymer) medium were manually mixed and then cooled. Formulations may be accomplished by one of two approaches: 1) as an intimately interpenetrating second phase of thermoplastic elastic material dispersed within the base viscoelastic material, or 2) as a collection of independent, discrete, elastic particles dispersed within the base viscoelastic material. Choice of particle size depends upon the application, and those skilled in the art of abrasive media honing can select the appropriate particle size for any given application. In some extreme cases it could exceed the volumetric concentration of abrasive particles. Free format text: Silicone rubber particles have affinity for silicone- or polyorganosiloxane-based media due to the tendency for silicone-silicone adherence and like specific gravity, both of which contributing to the tendency for the particles to stay relatively uniformly dispersed. For example, in long, narrow tubes media having enhanced elastomeric character can maintain a more uniform radial pressure distribution throughout the length of the tube compared with the distribution realized when using media which does not contain a thermoplastic polymer. By understanding the formulation code, a user can determine the characteristics of that media, and therefore intelligently select which media to use for a given operation. No. In a subsequent study, trial batches of media were prepared using six different formulations including silicone-based media, blends of silicone-based and thermoplastic polymer-based media, and thermoplastic rubber-based media. However, the term is commonly used to describe a substance that passes through a definite sequence of property changes as its temperature is raised. The abrasive media used in Abrasive Flow Grinding (also known as Abrasive Flow Machining AFM) provides the actual material removal: polishing, deburring and edge radiusing. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Some examples are: The carrier in this abrasive media has 57% by weight polymer, and will be relatively stiff. That is, this media provides a brighter more lustrous surface appearance, particularly on stainless steels components, with a slight loss in media aggressiveness. Enhanced elastomeric characteristics enable more uniform abrasive machining. In a particularly preferred embodiment, silicone- or polyorganosiloxane-based medium contains elastic silicone rubber particles dispersed therethrough to achieve increased relaxation times comparable to those attainable with the inclusion of a thermoplastic polymer. The liquified thermoplastic polymer and silicone rubber may be combined and blended during the heating of the thermoplastic polymer: the two components do not chemically react. Alternatively, at low percentage inclusion and with a significant percentage of mineral oil or other liquid carrier, the thermoplastic polymer abrasive flow medium can be formulated to achieve viscosities significantly lower than those of traditional media for honing applications where a more fluid carrier is preferred. Moreover, the thermoplastic polymer based medium used alone can accomplish uniform abrasive work in otherwise difficult applications such as along the entire length of long tubes. Abrasive particles may be incorporated in the present medium over a wide range of particle sizes and particle size distributions. EXTRUDE HONE CORPORATION, PENNSYLVANIA, Free format text: So, the researchers developed alternate media at low cost, easy availability. Abrasive flow finishing (AFF) is used to radius, polish, deburr and confiscate recast layer of components in anextensive variety of components. Traditional polishing methods originally involved manual filing or sanding or the use of rotary sanding and finishing tools. 60/584,590, filed Jul. In addition to the difficulty of conducting sanding operations in the interior or over complex surface features of a fabricated article, both manual and motorized sanding operations required a high level of dexterity by the artisan, the absence of which invariably resulted in erratic performance and unacceptable quality control. Other prior art methods such as vaporblasting, sand blasting, and shot blasting presented their own disadvantages, particularly in that none was of any significant utility in polishing interior fabricated surfaces. While the relative relaxation time (defined as the relaxation time divided by the residence time) for optimal processing will depend on various application-specific geometric characteristics and desired results, a relative relaxation time on the order of 1 or greater should be sufficient to produce measurable, beneficial results. An abrasive suitable for many applications is the aluminum oxide mentioned above. Generally, the characteristic relaxation time of the material is engineered to be comparable or large relative to the typical residence time of the material within the passage during abrasive flow processing. For example: WB46A-120S(60). For this reason, amounts for inclusion of thermoplastic polymers or particulates or silicone rubber particulates are not specified herein, because the desired characteristics are easily determined and implemented: the invention inheres in knowing to combine the stated constituents in the first place. Alternatively, the cooled thermoplastic polymer-based material may be shredded and compounded into other abrasive machining media materials such as silicone-containing materials. ScienceDirect is a registered trademark of Elsevier B.V. ScienceDirect is a registered trademark of Elsevier B.V. Study of Media in Abrasive Flow Machining and its Hybrid Processes. The resulting admixture was used in accordance with methods disclosed in previously mentioned U.S. Pat. By using the thermoplastic polymer alone as the carrier material, abrasive flow machining processes can be carried out in applications which cannot tolerate the presence of silicone rubber, or the silicone rubber may be enhanced by the additional presence of the at least one thermoplastic polymer.

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abrasive flow machining media

abrasive flow machining media

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